Patent GB-805694-A (GB)
Title: Telegraph switching system
IPC: H04L12/54
Filed: 1955-05-20
Abstract: 805,694. Telegraph exchange systems. STANDARD TELEPHONES & CABLES Ltd. May 20, 1955 [May 24, 1954], No. 14603/55. Class 40 (3). In a telegraph system comprising a central office having a plurality of outward communication channels arranged in groups, each group leading to one of a number of remote telegraph offices, and having a plurality of telegraph transmitters for passing messages over said channels, separate groups of manuallyselectable elements, with one element in each group associated with each respective remote office, are associated with each transmitter, switching means automatically connects any one of the transmitters at a time with any one of the said channels, and means responsive to the operation of any one of said elements is effective to control the switching means to associate its transmitter with one of the plurality of communication channels to the remote office represented by the operated element. In the diagrammatic arrangement shown in Fig. 1, the central office has two groups of three channels, A. B. C and A<SP>1</SP>, B<SP>1</SP>, C<SP>1</SP>, leading to each of the remote offices W and X respectively, two channels A<SP>11</SP>, B<SP>11</SP> to office Y and one channel A<SP>111</SP> to the office Z. Messages for transmission are received over lines A1, B1, C1 on printer perforators PPA, PPB, PPC having message tapes TA, TB, TC leading to three combined transmitter-distributers TDA, TDB, TDC individually associated with groups G1, G2, G3 of destination-selecting push-buttons PB. The operation of a button representing the office X in, for example, the group G2 associated with the transmitter TDB is effective to connect the transmitter to the control equipment CEX, associated with the office X and provided with selector switching arrangements which select the first available channel of the three channels leading to the desired station X. When a message has been received on one of the printers PPA, PPB, PPC, it is idled by tape feed-out means until the first character of the message is detected by the associated transmitter-distributer. At this atage the tape feed is arrested and a lamp illuminated to indicate that a message awaits transmission. The operator having noted the destination station operates the corresponding push-button PB which initiates the operation of the switching arrangement to seek the first available or free channel to the desired station. When a free channel has been found, lamps are illuminated to indicate this state of the connection and relays are operated to transfer the sending line temporarily to an automatic numbering machine which transmits the number of the message and a fixed preamble. A central station monitoring printer is also connected, and at the end of the fixed message, the numbering machine is disconnected, the transmitter distributer brought into operation to transmit the message and the signals for carriage-return and line-feed transmitted at the end of the first line are effective to disconnect the monitor printer. The end of the message is indicated by three carriage-return signals sent in succession, and the detection of these signals by a discriminating circuit is effective to control a series of relays which break the connection between the transmitter and the connected receiving station and which restore the circuits to normal in readiness for a further message from that transmitter distributer. The switching arrangement may be operated to select a free line of a group leading to a desired station on a rotational or a " firstavailable " basis. In the former case, if an engaged line, e.g. A, becomes free and a number of channels are simultaneously idle, the next message is transmitted over the channel next in order of sequence, i.e. B, but in the latter case, the earliest channel of the group, i.e. A, is used irrespective of the channel used for the previous message. Specification 658,959 and U.S.A. Specifications 2,587,253 and 2,632,044 are referred to.